I’m still a little confused in what cases does the catch block run in terms of trying an inter-canister call. Let’s say I have code: public func someFunc() { try { let result = await otherActor.otherFunc(); } catch e { // perform some action if other canister traps doSomethingInCatch(); }; } Wh…

Both. But if the try block fails directly with a trap (not in some async callee) the catch will not be executed and the enclosing method will, instead, immediately exit with the trap. The caller of the method will see this as a reject. Note that message sends can, in rare cases, trap synchronousl…

[image] kevinli: When does the catch block run? In which of the following cases (if any) does it run: Look at it this way: if any error happens for whatever reason in the try block, it should always go in the catch. At least that’s how a try / catch should work

That’s how it should work, but doesn’t. try { 1/0 } catch { return 42; } will not be caught. Unfortunately. But try { await async {1/0} } catch { return 42; } will. So as Claudio says: It can only catch when the canister receives a reject from another canister, or (I believe) if you throw expli…

[image] claudio: Note that message sends can, in rare cases, trap synchronously, before the message body is even queued and executed, which falls into the case of the previous paragraph. What are those rare cases? Looking at the interface spec The Internet Computer Interface Specification | …

I am also wondering how one can catch a synchronous trap in a message send. As a synchronous trap is rolled back, we will never know it happened. Can I wrap the message send into an asynchronous call?

[image] timo: Can I wrap the message send into an asynchronous call? Yes, I do this in the cycles faucet in a few places so that I have to do less error handling. But I wouldn’t put it anywhere where you are trying to squeeze everything out of your canister since the await may delay execution…

[image] Vivienne: Yes, I do this in the cycles faucet in a few places so that I have to do less error handling Do you a link to the code?

Must we always try/catch on calls to other canisters?

[image] timo: Do you a link to the code? Sorry, that one is not open sourced. But it’s nothing spectacular and I’m not even sure this is the proper way to do it. I use it as the lazy way out of doing more error handling like this: case (?coupon) { let now = Time.now(); if (coupon.expiry <…

[image] Vivienne: let deposited = await deposit_cycles_to(cycle_to_add, wallet); What does the definition of deposit_cycles_to look like? I suppose it is a shared function of the same actor. Does deposit_cycle_to have to be public? And does this really lead to a self-call that is queued by th…

When does the catch block of try catch run in motoko?

Developers

skilesare November 29, 2022, 1:32pm 15

A fast pass was added last year that let a canister continue execution if it was an await message to itself:

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When does the catch block of try catch run in motoko?

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